Controlled release of mercury into aqueous L-(-) histidine solutions : Biological implications of electrochemical studies

Abstract

Controlled release of mercury into aqueous L-(-) histidine solutions is examined in this study. The first effect of mercury on histidine is mercuration to yield two derivatives both of which are paramagnetic and contain monomeric Hg⁺ ion. In one of the compounds, mercuration is at the imidazole nitrogen while in the other it is at the alaninyl side chain. These two organornercurials undergo intramolecular transformations independently to yield urocanic and glutamic acids respectively. The net effect is the mercury-assisted deamination and oxidation of L- histidine. Urocanic acid also reacts with mercury to yield predominantly a Hg⁺ compound. The significance of the results to biological systems is considered. Monomeric mercurous mercury appears to be a potential intermediate·in mercury toxification process. UV-vis, IR and EPR spectra of Hg⁺ compounds are discussed in the light of the results from cyclic voltammetry and de and ac polarography.